Rift itself could be a great mode. The whole strategy of sticking together is great. That is where the good part ends.
The reset when a team gets a point. Whilst, it seems a good idea, it slows the game down far to much. Especially, when it's the first to 5. Maybe the first to 3? Or at least if a team goes 3-0 up. Make it a mercy? I mean if a team is good enough to go 3-0 up they're clearly higher skilled players. The lesser skilled are just spending a full match on a respawn timer. It can quite easily make people just not care. That ruins it for others.
I've been on both sides of 5-0. The best matches are the ones which finish like 2-1. Both sets of teams are about same in skill level. Unfortunately, those games only happen in like 1 in 10 times. Unless you can find a way to balance this then you need go back to the drawing board.
Many other games out there have variety of game modes but they also have maps suited to it. All your maps are 3 lanes. This really has a negative impact on certain modes. Maybe make some 5 or 7 Lane maps? Maybe more vertical? You need more variety to get round the map.